On 06/01/18 21:23, Thomas Gleixner wrote: > On Sat, 6 Jan 2018, Andrew Cooper wrote: >> On 06/01/18 11:49, David Woodhouse wrote: >>> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c >>> index 372ba3f..40e6e54 100644 >>> --- a/arch/x86/kernel/cpu/common.c >>> +++ b/arch/x86/kernel/cpu/common.c >>> @@ -904,6 +904,11 @@ static void __init early_identify_cpu(struct >>> cpuinfo_x86 *c) >>> >>> setup_force_cpu_bug(X86_BUG_SPECTRE_V1); >>> setup_force_cpu_bug(X86_BUG_SPECTRE_V2); >>> +#ifdef CONFIG_RETPOLINE >>> + setup_force_cpu_cap(X86_FEATURE_RETPOLINE); >>> + if (c->x86_vendor == X86_VENDOR_AMD) >>> + setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD); >> This isn't safe. It needs to be dependant on finding that LFENCEs are >> actually dispatch serialising. >> >> In particular, when virtualised, you'll most likely be saddled with the >> hypervisors choice of setting, in which case you need to use retpoline >> as a fallback. > On bare metal we are sure, the virtualization part is a different question.
Leaving virtualisation to one side, how does this cope with pre-SSE2 hardware? ~Andrew
